This is a four post article due to posting size limitations.Key Words: GOES, Geostationary Weather Satellite, HRIT, LRIT

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Geostationary weather satellite image reception is more challenging than APT weather satellite image reception, but can be achieved well using an SDRplay RSP2 as described here. Before getting started in putting together a receiving system for HRIT and LRIT images, it is a good idea to go through this article and get a good idea of all of the software, components, and related expenses. The HRIT and LRIT images available from the GOES 13, GOES 14, GOES 15, GOES 16, and similar satellites are really spectacular. The file size limitation for posting images on this site significantly reduces the available resolution. Complete images can be 40MB in size.

GOES 13 FD Colorized Image.JPG (200.24 KiB) Viewed 11187 times

The above is a GOES 13 LRIT image received with the loop Yagi antenna and USA-Satcom XRIT decoder software; the gray-scale image has been colorized using Adobe Photoshop™.

Part of the challenge in setting up a geostationary weather satellite image receiving system is in determining where your position is in relation to the various geostationary satellites. One way to get an idea of the satellite’s position is to apply Orbitron software and select the geostationary satellite of interest and look at its position in relation to where you are. This will help you visualize approximately where to point the antenna. Orbitron software is available here: http://www.stoff.pl/.

In a typical setup, a 1 m diameter parabolic reflector antenna or equivalent (20dbi to 22dBi gain) works well. However, if you are nearing the outer fringes of the reception area, you may need up to a 2.2 m diameter parabolic antenna or equivalent (around 28dBi gain). To give you a rough idea, a 1 m wide parabolic grid reflector antenna such as the L-Com Hyperlink Brand HG1922EG having 22 dBi gain has been used with good results receiving GOES 13 LRIT and GOES 16 HRIT images from areas across the continental United States. The loop Yagi antenna described here and in the prior HRPT image reception article also works quite well (viewtopic.php?f=5&t=2624) for receiving GOES HRIT and LRIT images. With either type of antenna, you will need a good LNA such as the TriQuint/Qorvo TQP3M9037-PCB evaluation PCBA which provides approximately 21dB gain with a noise figure of 0.36dB when operating in the 1.69 GHz range. The LNA in the image below has been modified to apply a 10uH inductor 220 mA (PN 9250A-103-RC) and 33uF 25VDC capacitor (PN TAP336K025SCS) to supply power via the coaxial cable from the RSP2 using the RSP2’s BIAS-T feature on Antenna Port B. The TriQuint TQP3M9037-PCB evaluation PCBA only requires around 47mA at 5VDC. Operation off of the RSP2 Bias-T power can be used, if a band pass filter is not needed in your area. Be sure to use flexible (to allow the antenna mount to move properly), low loss cable, such as LMR-240 to connect the LNA (and filter, if a filter is used) which is used to go the short distance to the RSP2 (or a line driver, if the RSP2 will be mounted far away from the antenna).

TQP3M9037.JPG (55.22 KiB) Viewed 11187 times

If you live in an area with high levels of terrestrial interference near the frequency of interest, you may wish to further employ a filter such as a Sysmocom or similar L-Band cavity filter with a pass band of 1525 MHz to 1750 MHz. If you place a filter between the LNA and the RSP2, you will need to provide 5VDC power directly to the LNA and may not wish to apply the Bias-T modification described above, since the filter will not pass the DC voltage through.

The Meade DS2090AT telescope mount with a 497 controller was repurposed for use as a tracking system and mount for pointing a loop Yagi antenna to geostationary and orbital satellites. The L-Com antenna described above will be too heavy and bulky for proper use with the Meade DS2090AT mount, so a different mount would be used with the L-Com antenna. If you use a loop Yagi and the Meade DS2090AT, be sure to obtain the latest DS2090AT version which has a blue band around it showing the position rather than a black band. Older versions of the mount may not work as well without some modification for this application (they may slip in vertical movement, given that the loop Yagi antenna having 26 director elements is near the maximum out-of-balance weight for the mount – if it should slip and tightening does not solve the problem, pull the vertical control portion apart and insert a rubber washer such that it is between the friction plate and the original gripping section; alternatively, you may be able to add some non-metallic weight to the back of the boom to better balance the antenna in the mount). Given that the diameter of a 90 mm telescope tube is near that of the loop Yagi in the 1.69 GHz range and the antenna weight is comparable to that of a telescope tube, making use of a used telescope mount capable of tracking satellites worked well in this instance. Meade Instruments has downloadable software on its web site to allow uploading the most recent versions of software and TLE (satellite data) files to the 497 controller using an RS-232 serial cable. Refer to the Autostar™ Software Updater. Additionally, Meade has downloadable Autostar™ Suite software to enable using the DS2090AT mount to point to any position in the observable sky for geostationary satellite image reception as well as to track orbital satellites passing overhead. With the Meade DS2090AT telescope mount and 497 controller, once the setup has been initialized, you can point the loop Yagi antenna directly to the geostationary satellite of interest.

The antenna used is a 26 director element (30 total element) loop Yagi antenna with center frequency at 1.69270 GHz. The antenna is applied for reception of HRIT/LRIT signals from geostationary weather satellites (and has also been successfully applied for receiving HRPT orbital weather satellite images). Depending on your location, it may be useful to apply additional loops (e.g., 32 director elements) which will unbalance the DS2090AT mount so you will also need to apply some additional weight on the back end that does not interfere with reception. At 26 director elements, the antenna is at the limits of what the mount can support without additional weight on the backend to counterbalance the antenna. Using any type of metal to mount the antenna anywhere near the director elements will result in decreasing the gain of the antenna. This is why the antenna is mounted from behind the first reflector element. Using the standard Meade telescope clamshell to hold the antenna required additional reflector elements to offset the effects of the clamshell fixture on the signal and optimize the gain when the loop Yagi antenna is mounted. The antenna mount is made from a PVC connector fitting that is made to connect two 3” PVC pipe ends. The PVC connector fitting was obtained at the local hardware store. You will need to modify the PVC connector fitting by using a drill with a small grinding head to remove enough of the inner rim to allow the antenna boom to fit tightly against the inner wall. You will also need to drill two small diameter bolt holes through the PVC and antenna boom and mount the boom inside the PVC with two bolts; make sure these holes are just barely wide enough to allow the bolts through (any excess will allow for play in the movement of the antenna when mounted and any potential play or variability in position needs to be kept to a minimum). Additionally, you will want to use some industrial strength glue to attach hard plastic alignment pieces on either side of the boom on the inside of and attached to the PVC fitting, following the boom and firmly up against it, but not glued to the boom. This will keep the screws from eventually widening the holes in the PVC and creating a loose fitting, once in operation. The antenna boom is long enough and heavy enough to put significant force on the mounting screws and PVC where the screws are mounted when moving, so you will want to keep the antenna boom from shifting where the screws attach the antenna boom to the PVC. The PVC is then removed and painted to prevent deterioration in the environment; then the PVC is reattached to the antenna boom firmly. Next, you will need to find 1/16” thick by 1” wide rubber strips, preferably with an adhesive backing to attach around each end of the PVC fitting. This will allow a firm fit in the 90mm clamshell mount. Do not remove the existing felt padding inside the clamshell. Now you can mount the antenna boom with attached PVC to the clamshell. Mount the linear-feed loop Yagi antenna based on the polarization of the satellite intended for reception. Note that a diagonal polarization position works well enough so that you are not having to continually axially rotate the loop Yagi antenna for satellite signals from GOES 13, 14, and 16. You will need to axially rotate the antenna to receive images from GOES 15 noting the required polarization for GOES 15. The boom used is a ¾” diameter and 6 ft long aluminum tube. Holes were drilled in the boom as indicated in the table below. The loops for the loop Yagi antenna were made from aluminum sheets and carefully cut to size with holes drilled at each end for mounting. Mounting of the loops, excluding the driven element was performed using aluminum rivets. The driven element was attached by drilling a hole through the boom to pass the UT-141 through and the UT-141 (after attaching the SMA connector and bending to mate with the LNA) was then attached to the aluminum boom. This can be done, such as by using a small amount of conductive epoxy on either side of the boom where the UT-141 enters and exits.

Once you have your antenna and LNA setup and connected to the RSP2, you are ready to receive the HRIT or LRIT signal. Start with GOES 13 at 1.691 GHz, if you are in the central United States and you should see the following LRIT signal using the 8Msps setting for SDRuno:

The above image shows the GOES 13 LRIT signal while data is being transmitted. For good image reception, you should have an SNR of at least 6.5 dB. To obtain a good view of the signal with SDRuno software, you will need to increase the FFT Ave to at least 64. The above image was taken with FFT Ave set to 128. The below image shows the GOES 13 LRIT signal in its idle state.

Once you are receiving LRIT signals well, swing the antenna to GOES 16 for HRIT signal reception. You should see the following signal at 1.6941 GHz:

HRIT SDRuno.jpg (94.4 KiB) Viewed 11185 times

Once you are ready to receive LRIT and HRIT images, you will need image decoding software. HRIT and LRIT decoding software is available via GitHub from the OpenSatelliteProject. Alternatively, you can obtain a ready-to-use version of HRIT and LRIT decoding software that runs under the Microsoft Windows OS for a fee through USA-Satcom. The HRIT and LRIT images presented in this article were generated using the USA-Satcom XRIT decoder software. The image decoding software does require more processing power than that used to decode APT images from orbital satellites. Contact USA-Satcom for the suggested CPU speed and memory requirements to properly process HRIT and LRIT images using the XRIT decoder software. USA-Satcom can be contacted here: http://usa-satcom.com/contact/. Here is an example image of the USA-Satcom XRIT decoder software under operation with the RSP2 and loop Yagi antenna for GOES 13 LRIT image reception:

99.5 Q FEC 7.JPG (85.79 KiB) Viewed 11185 times

Once you have the setup running well (a signal quality of 97% or better), the HRIT and LRIT images transmitted by the GOES and similar geostationary satellites are amazing. Below is a cropped GOES 13 image of the eclipse that crossed the United States on August 21, 2017:

Additional information on the PVC mounting bracket. Here is the PVC mounting bracket with plastic guides glued in. A portion of the center ridge has been removed to allow the boom to lay flat against the inner wall.

Mounting Bracket 1.JPG (84.04 KiB) Viewed 10404 times

Here is a picture of the painted PVC bracket with 1/16 inch thick rubber tape applied to the outer edges to allow for a tight fit in the clamshell holder of the mount.

Mounting Bracket 2.JPG (78.13 KiB) Viewed 10404 times

Here is a picture of the loop Yagi antenna attached through the PVC mounting bracket. Note that the PVC mounting bracket is exactly centered between reflector elements 1 and 3.

Additional notes: Total loop Yagi antenna weight is 11.6 ounces with 26 director elements (30 total elements). The DS2090AT mount works reasonably well with an unbalanced load up to around 10 ounces of unbalance. The telescope tube that is normally used with and typically balanced on the mount weights 55 ounces (3.4 lbs). The loop Yagi antenna in this article is not balanced on the mount. Mounting it at or near its balance point on the half metallic clamshell causes a reduction in gain, so the loop Yagi antenna from the first reflector element forward is mounted in front of the clamshell.

If you order a 50 ft USB cable and it does not have a large ferrite bead on each end and an active transceiver in the middle, it may not work well for this application. Be aware of this when you order a USB extension cable for SDR applications. Check the properties of the cable with the company offering the cable, before you purchase one.

Be sure to check NOAA operation schedules for GOES 13, 14, 15, 16, and newer GOES (and other LRIT/HRIT capable) satellites as these are launched. As of the past week, GOES 16 has been moved to a new position effectively replacing operation for GOES 13. Here is an image from GOES 16 in its new position. Note that the white background was converted to black for aesthetic purposes using image editing software. The easiest way to do this is to open the image in Paint, then select black as the fill color, then select the fill icon (looks like a paint bucket pouring paint), then click on the white background, then save the image.